Flat screen



INVENTOR? 2 Sheets-Sheet l 1 C. L. DURKEE FLAT SCREEN Filed Aug. 4, 1934 Sept. 22, 1936.

ATTORNEY Patented Sept.'22, 1936 1 2,054,968

UNITED STATES PATENT OFFICE FLAT SCREEN Clarence L. Durkee, Wausau, Wis.

Application August 4, 1934, Serial No. 738,420

7 4. Claims. (o1. 92-32) This invention is concerned with the paper inin general practice amounts to only a fraction dustry and resides in an improved fiat screen of an inch, the rate of alternate displacement wherein the immediate structural support of the is rather high and the weight of fluid above the vibrating diaphragm bottom members serves also bottom is substantial. Due to this high rate as the support and reaction-absorbing member and the rather high inertia of the fluid under- 5 of the vibration-producing mechanism. -The going acceleration, momentary stresses of high machine of this invention is adapted to the use intensity and high frequency are continually of high strength materials, and the use of proproduced in the machine. The reaction of the tective linings for preserving the life. of the stresses in machines heretofore employed must be 10 equipment and preventing contamination of the carried back to the cam support, eccentric, or 10 material which is to be treated. rockshaft, which constitutes the vibrating mech- Flat screens, as they are known in the'art, are anism per se through the long, bridgelike supwidely used in the paper industry. In these port of the trough, down a column, and thence devices the essential member is a slotted plate across the girt as the support of the vibrationhaving very fine openings. -This plate is 'supproducing mechanism is called. 15 ported between the bottom and the top of an These stresses operating on long moment arms open trough. Pulp which is to be treated is produce large moments at the points of support, delivered into the trough suspended in water. which accounts satisfactorily for the rapidity The bottom of the trough beneath the plates is with which the structures are known to deteof a flexible construction zand is vibrated at a riorate. -Flat screen vats have heretofore been 20 rate of approximately 500 to 1000 alternate disconstructed largely of wood and the flexibility placements per minute. This produces an alterinherent therein probably accounts to a large nating flow of fluid through the slots in the degree for whatever practicability they may plate which, nevertheless, due to the method of possess. With the high alternate stresses, how- 5 feeding and drawing off product, on the averever, and the flexibility ofthe structure, vibraage amounts to a downward flow. The oscillation difficulties are not only rife throughout the tion of the fluid in the slots of the plate is esmachine, but extend to the problem of supportsential to the bringing about of an orientation of ing the machine itself and the buildingswherein the fibres such as will permit passage thereof the machine is housed.

0 through the plate as well as the continued clear- In the machine of this invention, however, the ing of the plate openings of that objectionable reactive supports of the vibration-producing portion of the pulp of excessive coarseness, mechanism itself are associated with and made which is to be ultimately disposed of by an overpractically integral with the immediate strucflow which is continually maintained above the tural support of theflexible bottom and in this plate. The main portion of the fluid and pulp, way reactions produced by the accelerations of 35 however, which passes downwardly through the the fluid are absorbed in the immediate neighplates is carried away continuously from open- .borhood where created and are not permitted ings between the plates and. the vibrating botto travel through a long, bridgelike portion of tom. -the structure, thence downwardly through col- 40 Many variations in form have been employed 'umns, and back through the floor or the girt to 40 in the construction of flat screens and from the vibration-producing mechanism. In this 7 time to time substantial improvement therein way r'eactions arekept sufiiciently closely assohas been made. However, priorto the time of ciated so that elastic deformation of parts is this invention there has'been one structural reduced to a minimum and a measure of dyfeature in common with all the variations, namic balancing of the structure is obtained. 45 namely; that the immediate structural supp rt, Due to the elimination of prohibitive stresses of the vibrating diaphragm bottom has been and the suppression of vibration, highly rigid formed as a part of a rather long, troughlik materials, such as steel, may be employed, crevat, which is supported by legs or similar supating a structure of high strength and rigidity,

ports at extended intervals, while the mechaand t u permitting the O Bnt 0f the ma- 50 nism which produces the vibrating movement chine in a relatively permanent type of struchas been supported on another independent ture in contrast to rapidly deteriorating Wooden structure placed entirely below the vat or on structures heretofore considered essential. In the floor. 7 this way all the disadvantages of wood, includ- Although the displacement of thediaphragm 'ingfits propensities to become Water-soaked, and 55 principal supporting members. .are shown in Fig. 1 as the side-supporting chan tically indestructible lining materials, such as' rubber, lead, Monel metal, and the like, may

easily be incorporated, altered, or replaced -with- I out the necessity for any new construction or new fittings of any sort. If the rubber diaphragm beneath a particular frame becomes damaged, its replacement may be accomplished simply and without disturbing the remaining machine. The edges of the diaphragm are not exposed to fluid and, therefore, fabric is not destroyed or attacked.

The machine of this invention is best described by reference to the accompanying drawings, wherein Fig. 1 shows a side view of the machine, portions being broken away;

Fig. .2 is asection taken at the line 22 of Fig. 1;

Fig. 3 is a section taken at the line 33 of Fig. 1', showing details;

Fig. 4 is a section taken at the line 4-4 of Fig. 3, showing details, including a modified form of sealing strip;

Fig. 5 is a section taken at the line 5-5 of .Fig. 2, showing details;

Fig. 6 is an enlarged detail view, with portions broken away, of the eccentric.

As shown in Fig. 1, the machine of this invention is characterized by its self-contained appearance arising out ofrthe fact that the vat proper as well as the rock-shaft, or any other vibrating mechanism or medium and diaphragm connections, derive their support from the same These members nels I and 2. The channel I has been broken away with other parts of the machine to reveal a'sectional view on the left of Fig. .1, but both channels'run from a supporting pier 3 to a supporting pier 3 and form the principal supporting members of the'entire machine and give it the desired elevation. The channels I and. 2 are aided-in their function "as supporting members by the vat sides 5 and 6, shown best in Fig. 2. The vat sides 5 and 6 are' formed of strong, structural, channel shapes which extend throughout the length of the entire machine. The vat side 6 is spaced apart from the support member 2 by outlet boxes 8, which will be described more in detail. Said outlet boxes 8. are arranged at intervals and between the same are through-bolts l which pass through the webs of channel 2 and vat side 6, binding these members securely against the upper and lower sides of the outlet boxes -8, thus uniting the entire side of the machine into one practically rigid member. The other vat side 5 is spaced from the support member I. Between thetwo and uniting the same into one practically rigid member are sectional diaphragm clamp angles 9 which are bolted to the vat side 5 by bolts I0,

holding therebetween flexiblediaphragms I2, to

bedescribed more in detail, and also bolted to supporting member Iby bolts II. The clamp shaft 36.

angles 9 are in short sections, as shown, and are easily removable by removing bolts I and II. The two sides of the machine are thus shown to consist of two rigid arrangements of high strength.

At intervals, as shown in Fig. '1, the supporting members I and 2 are joined by cross-tie members I3, which are in the form of T section structural shapes. The cross-ties I3 are rigidly riveted to the supporting members I and 2 by rivets and angle brackets-I4. At the extremities of supporting members I and 2 there is ,securely riveted in place an end channel I5, as

' ties I3 not only adds further to the rigidity of the entire 'machine, but also provides for the support of a rock-shaft or vibration-producing mechanism. Securely bolted to the cross-ties i3 and the end member I are pillow block bearings .I;.6,,I:.'I, .IB, .I,9;and 2E1. These are coaxially aligned for the rotational support of a rockshaft 22 ,Shaft 22 is. formed from a'square steel bar, as better shownrin ,Fig. .2, having cylindrical sections formed therein, as shown by the dotted circle in Fig. 2., ,The cylindrical sections are located to coincide with bearings I6, I1, i8, I9, and 2.0. Therock-shaft 22 thus derives its entire support 'directly from the main supporting structure of'the entire machine. 7

The vibrating movement in this particular .case, .although other methods may likewisebe .employeid, such as cams, etc., is communicated from the rock-shaft 22 to the diaphragm assembly through rocker ,arms 23-23 and 2 5. Rocker arm '24 is, clearly shown in Fig. 2 and .is shown as consisting of two sections divided .along a diagonal of shaft 22. The two sections are .adapted to be drawn tightly against the shaft'ZZyby bolts 25 ,-making it possible to maintainthisbonnection absolutely secure regardless of wear., One'of the sections of rocker 24 is furnished-with a jaw-clamp and clamping screw .21jforsecurelygripping the rocker pin 26. The other section of the-(rocker arm 24 is furnished with ;the;socket portion 28 of a ball and socket joint. ,Seated within the socket 28 is a ball 29 :whichzis carried ,upon upper female part 30 of .a .-right-=.and,1left-'hand screw coupling 3!. The lower :female portion of the coupling isformed integrally'zwithihe .casing32 of a variable eccentric.

The variable eccentric is shown in detail in Fig. 6. .It comprises thecasing 3.2 in which a bearing-i33 is .held in place by the keeper plate 34. The bearing :33 surrounds an eccentric sleeve B5'having abore eccentrically placed with respect 'to its cylindrical outer surface upon which the bearing 33 rests. The eccentric bore fits snugly upon a main eccentric shaft 36 so that theeccentric sleeve may turn thereon to vary'the effective eccentricity of the outer cylindrical surface-of the sleeve 35. The sleeve 35 is provided witha-shoulder which faces a flange 31 formed integrally with the main eccentric Studs '38 pass through the flange 31 into the shoulder of the eccentric sleeve 35 main eccentric shaft 36. The main eccentric shaft 36 is journaled to turn in bearings 39, the

latter being secured to the floor, as shown in 'full'lines in Figs. -'1,*'2, and 6,0r, if preferred, to the main frame of the machine, as shown in dotted 'lines in -'Fig.'-2,-or in any other conven- 35 eccentric shown in dotted lines or its equivalent members.

is to be preferred. However, in'many cases this may be neither necessary nor desirable.

V The rocker arms 23 above referred 'to and shown clearly in the drawings are'similar-in all respects to the rocker 24 except that no socket portion is employed. Therockers 23-43 and 24 are arranged in alternation so that rocker pins 26 fall alternately upon the right and left sides of shaft 22.

, Diaphragm shoes 49 are pivotally mounted on rocker pins 26 and extend upwardly therefrom to form flat, horizontal, rectangular surfaces between the vat sides. The diaphragm shoes are arranged in right and left-hand order corresponding to the placement of the rocker arms v23---23 and 24, as appears in Figs. 1 and 2.

Above the diaphragm shoes and clamped securely thereto are flexible rubber fabric diaphragms i2, heretofore referred to. The diaphragm material is of a construction strong enough so that the diaphragm shoes combine therewith in such manner that these two members furnish one another mutual support and no guiding of the diaphragm shoes 40 is necessary other than that furnished by the diaphragm l2. 7

The diaphragms 12 are clamped to the lower portion of the vat so as to completely seal the same except for the outlet boxes 8. As shown in Figs. 1 and 4, the vat is divided into frames by bearers 4| which are placed crosswise at intervals between the diaphragm shoes 40. As shown clearly in Fig. 4, the bearers 4| are furnished with a spreading base through which bolts pass downwardly through the diaphragm l2 and clamping angles 42, Where they are tightly held in place, by means of nuts, thus forming a rigid, water-tight'connection between the diaphragm l2 and the bearers 4!. ,As shown in Figs. 2 and 3, the diaphragm [2 extends outwardly between the vat side 5 and the clampangles 9, thus providing a combined, water-tight connection and support. The outlet boxes 8 extend into the vat, one into each frame, and carry a flange abutting at each end against the sides of the bases of bearers 4| and having its lower surface flush with the lower surface of the bearer bases. The remaining side of the diaphragm I2 is brought to a rigid, water-tight connection with the flange of the suction boxes 8 by bolts 43 and clamping bars 44.

The screen proper, composed of plates 45, is clamped into the vat in water-tight connection therewith. For this purpose, transversely dividing each frame, are the struts 46, having a dove-tailed boss transversely formed in the upper side thereof. The beveled edges of the plates 45 are placed under the dove-tail, as shownmost clearly in Fig. 4. The plates 45 extend over and rest upon the upper surfaceof bearers 4|, a gap occurring between adjacent margins of consecutive plates. Into these gaps Wedge bars 41 are inserted and are forced'downwardly into place by hold-down screws 51, which are mounted in replaceable, inclined blocks58, as shown most clearly in Fig. 3. The plates 45 are thus wedged and held longitudinally in water-tight connection with their supporting To insure water-tightness along the margins of the plates facing the vat sides, sealing strips 50 are employed. The sealing strips 50 ened by'lbolting the clamp are likewisesecurely held in'plac'e by l'iold-do'wn screws 55 'acting in i'nclined blocks '56. In the case o f the inclinedblocks 58 and 56, an inclined projection is provided on each, which acts against an' apertured plate letinto the trough sides 53-; The action of the blocks 56, therefore, is to simultaneously jam'the sealing strips 50-against1the edges'of the'plates 45 and against the trough'sidefmembers 53. A sealing felt 5| insures fa le'ak pr'oof connection. The inclined blocks 56 'and'58 are easily detachable and may be quickly replaced in case of breakage or stripping of the threads. The sealing strips 50, as shown in Fig. 1, completely conceal the blocks 58 and thescrews 55, as shown best in Fig. 2, are the only projections. This contraction tends to eliminate accumulations of pulp which decompose-and contaminate the product, because there are very few projections where pulpmay accumulate. r

In Fig. 4 another form of sealing strip is shown. In this cake yokes 49, which are replaceable, serve as a mounting for the holddown screws 48; The screws 48 force the locking bars 41 in place and also carry a jam nut which acts against the sealing strips 59, holding the same securely in place against the jam cords 6B.

The bearers 4|, struts 46, outlet boxes 8, screen plates 4 5, 'and the like, are suitably formed from "materials welladapted to resist corrosion and 'for this reason the only structure not-conveniently or economically formed of non-corrosive material are the two vat side members 5 and 5. However, they may be of steel and suitably lined. As shown in Fig. 3, a protective coating in the formof a lead or cadmium, adhering, or other suitable coating may be provided with the greatest ease and convenience, or, if desired,'the element 55 may be non-adhering sheet material ofwhatever composition the particular material being processed demands.

As shown in the drawings, the rock-shaft 22 is supported securely by the same structural members which'pro'vide the support for the diaphragm. The reaction, therefore, resulting from the 'acceleration'of the fluid is communicated directly to the rigid sides of the machine and thence back to the shaft 22 without having to travel more than the space of one frame. In the cas'e of a flat-screen, which may be adjusted for'very strong'agitation, the return of the reaction to the shaft'22 may be even further shortangles 42 securely tothe'fcros's-tie members 13." In case of a desire to produce a machine ascornpletely rigid and immovable -as possible, cross-ties l'3 may be placed together with bearings I! at each division between frames and securely bolted to the clamp 'ang1es 42. However, this expedient is not always essential, as is shown in Fig. 1, partly because of the fact thataltern'a'te diaphragms are pursuing opposite-movements and in this manner joifset and bala'nee-"one-another to a certain extent. As shown in Fig. 2,}the eccentric may be formed as a part of the frame of the machine and by so'doing no reaction between the floor and the machine proper occurs. As pointed out above, thismethod of supporting the eccentric may be'resorted to when it is desired to protect the building in which the machine is housedfrom vibration as far as possible 1 I From the above and from the self-contained nature of the machine,las appears in the drawingsand' in the description, the advantages of the ma h e o thi i ven on o e thos he e tofore m yed e num rous.- Q adram tage resides in the fact that it is ,often con.- venient to pitch the screen in one direction or t er. 7 in wh ch case with, th ma mn o this invention the ball and socket joint -;28. -.-,29 accommodates for the angularity introduced by the pitch. In machines heretoforeiiseda separate adjustment of the lengthpf each conn'eete s-r a W as vfo -ane la ty was n cessar in case the inclination of the screen was different from that of the floor. In cases where the eccentric is mounted on the frame of the machine itself these diincnlties are also entirely obviated.

Although other appropriate means for oscilla the p asmsmey b e oy d wi equal success in the machine of this invention, only one specific means for accomplishing this purpose is shown, namely: a rock shaft. rock-shaft, however, of itselfis possessed of certain advantages i arising, out of the employment of a squared sectionand the manner of clamping the rocker arm members thereto. ,In this way set-screws and keyways, thatare susceptible to wear and looseness, as have here-toiore been employed, are eliminated.

The eccentric employed may be variedas .to=its stroke, as showninFig. 6, and.explained above and this is of a substantial advanta e inobtaining the maximum effectiveness from the screen. For example, when a long, hat screen ,is :employed, having about twenty-four ,er more frames, it is often advantageous ,to oscillatethe diaphragms in different sections in different manners so that the more decidedly improper portions of the pulp may bequielgly eliminated by rapid agitation in that part of ,the screen which treats the pulp first and-a more gentle, discerning treatment can be provided at the final-end of the screen.

When screens are arranged in long structures the joining of the ends of the ,members is an important matter. Themachine of this inven.- tion being adapted for-construction of ,steeL-it is particularly well -adapted for vthe jeinin'g .of the members end to end by welding ,or splicing without loss of space. In the-fiat sereenshereto fore employed thesplicing of the vWQQlen ends has been a problem which has not been satisfactorily solved. The splices notpnlyare dinicult to make, but do not remaintightfor more than a rather-short-period. lnethe screen of this invention the joining of the S6121OI1S may be accomplished easily and when completed these joints will remain secure through the entire life of the machine.

If two lines of screens ,-are arran ged parallel to each other in close p;re ximity, a-single eccentric placed between the machines can be empl y d t uat :th oc -sh f mec ani m o both machines. Inthis way-two;.machines may be counterbalanced one against the other, providing a further ;means for the elimination of vibration.

The usual form of construction nowemployed through the entire. screen employed- .5133. so

doing a substantial 1 reduction 11-11 :the jmaterials of the machine substantially lessened. In such cases .twmdiaphragms, limited in extent only by the strength of the materials employed, may be balancedone against the other and the machine operated fully in accordance with the disclosure of this invention.

A further advantage of this invention lies in thefact that itis a simple matter to reduce the distance between diaphragm and screen plates to a minimum and it has been found when this distance has been reduced to three inches or less a great reduction in inertia of the fluid to be moved permits of substantial saving. In such a .case the load on bearings and other movingparts, as Well as upon the supporting structure, .is diminished to such an extent that a far lightensimpler, and more economical constructionmay be employed with no loss of capacity or any diminution of the high Velocities which are necessary to purgeand prevent lodgment of pulpand lumps in the screen plates or the cells of the vat.

In the machine of this invention the diaphragm edges are carried to the outside of the machine and there is no liquid in contact therewith. This is of importance in that the fabric core of the diaphragm materal has a tendency to act as a wick and to carry moisture into the interior of the material, causing rapid deterioration thereof. The diaphragm is held also chiefly ,by members which are not exposed to the liquid, and these may be made of ordinary materials in so far as corrosive efiect is concerned and, consequently, can be more cheaply made.

While the above description and the accompanying drawings have been employed to describe in detail the machine of this invention in connection with one specific embodiment thereofl it is intended thatprotection of Letters vPatent to be granted hereon be not necessarily limited thereby, but extend to the full scope of the invention as represented by the claims appended hereto.

What I claim is:

1,. In amachine of the character described, the

tioned under said cross members, anoscillatable rockshaft having squared portions carried by said ,bearing cross supports, rocker arms .clampedto said squared portions of said shaft, and diaphragm shoes actuated by said rocker arms to communicate an oscillating movement to said ;diaphragm. Y

3. In a ,machine of the character described, the combination comprising longitudinal supporting members, cross members therebetween, screenplates mounted thereon, diaphragms se- ;c ured thereunder, bearing cross supports posi- -tiened under said cross members and secured to said longitudinal members, an oscillatable-rockshaft carried by said cross supports, rocker arms ecured to said shaft, diaphragm shoes actuated 145 combination comprising longitudinal supportby said rocker arms to communicate an oscillating movement to said diaphragms, and an eccentric mounted upon said longitudinal supporting members and connected with said oscillating shaft for the actuation thereof.

4. In a machine of the character described, the combination comprising a vat, screen plates therein, diaphragms disposed the'rebelow, vibration-providing means for actuating said diaphragms, vat sides surrounding and extending above said screen plates, apertured bearing plates secured to said vat sides, wedge bars holding said screen plates in position, jackscrews bearing against said wedge bars and having a hook portion engaging some of said bearing plates, sealing strips at the juncture of said vat sides and said screen plates, and jackscrews bearing upon said sealing strips and having an inclined hook portion engaging some of said bearing plates so that said jackscrews exert a combined downward and outward pressure against said sealing strips.

CLARENCE L. DURKEE. 

